CCleaner v 2.15.815 works fine in every respect on my XP computer (even with Firefox) except that on one of my family sign-in's. It starts to clean and then disappears without trace. I have uninstalled and reinstalled, and done lots of things like I tried it in various combinations of other open sign in's but it is defiantly not wanting to work on that account. Details XP 2002 SP3, Pentium 2.40GHz 1GB RAM, plenty of free disk. Problem started about a month ago, been very happy with the product for 6 months before that.